Isolation And Characterization Of Mucinlike Glycoprotein Associated With Photoreceptor Cells

PURPOSE. Although previous lectin-histochemical studies have shown that O-linked glycoproteins are distributed in cone pedicles and rod spherules, as well as in photoreceptors, including associated interphotoreceptor matrices (IPM), attention has been directed only to those in the IPM. In this study, cloning of the O-linked glycoproteins not only in the IPM but also in the region including the cone pedicles and rod spherules was attempted.METHODS. The cDNA for the core protein of the O-linked glycoprotein in the bovine retina was isolated by screening a bovine retinal cDNA library using a polyclonal antibody against the jacalin (a lectin specific for O-linked sugar residues)-binding glycoproteins (JBGPs) in the whole bovine retina. The expression of the JPGP core protein in the retina was examined by means of in situ hybridization histochemistry and immunohistochemistry.RESULTS. The cDNA was isolated and found to encode an entire core protein [predicted molecular mass (M-r): 101 kDa; rich in Ser and Thr; mucin-like] for the JBGPs with M-r of 120 and 135 kDa. The mRNA was expressed in both cone and rod photoreceptor cells. This protein was distributed in the cone pedicles and rod spherules as well as the photoreceptor layer.CONCLUSIONS. Mucinlike glycoproteins with M-r of 120 and 135 kDa may be synthesized in the cone and rod photoreceptor cells, respectively, and distributed not only in the photoreceptor layer (probably including the IPM) but also in the cone pedicles and rod spherules.